DE3208662A1 - METHOD FOR PRODUCING PETROLEUM FROM DEPOSIT WITH THE HELP OF CARBON DIOXIDE - Google Patents

Description

SHELL INTERNATIONAL RESEARCH D-8000 MUNICH 90

MAATSCHAPPIJ B.V. SCHWEIGERSTRASSE 2

Carel van Bylandtlaan 30 /. ,

_ _IT .... . , phone: (089) 6620 51

The Hague, Netherlands ^Vl '

TELEGRAM: PROTECT PATENT

1A-55 59 2

Description:

Process for crude oil production from deposits with the help of carbon dioxide

The invention relates to a liquid-operated method for oil production, in which C0 _? , surface-active substance and water is injected into an underground petroleum deposit, the surface-active substance used for the process being a special member of a chemically relatively highly stable and salt-resistant class of surface-active substances.

Numerous patents have been issued for substances and techniques pertaining to a petroleum production process in which CO ₂ , surfactant and water are injected. U.S. Patent 2,226,119, issued December 24, 1940; U.S. Patent 2,233,381 published February 25, 1941 and U.S. Patent 2,233,382 published February 25, 1941 describe polyalkoxylated alcoholic or phenolic surfactants commonly used in aqueous liquid, liquid-operated oil production processes. US Pat. No. 2,623,596, published December 30, 1952, shows that additional oil production can be achieved by a process in which highly compressed liquid CO _{2 is} injected. US Pat. No. 3,065,790, published November 27, 1962, describes that the cost efficiency of the highly compressed CO ₂ can be improved in a liquid-operated process by first injecting part of the CO ₂ and then a cheaper drive fluid. U.S. Patent 3,330,346,

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3 2 0 3 6 6-2

1A-55 592 £.:

published July 11, 1967, shows that almost every method of foam formation within a deposit can be improved if a polyalkoxylated alcohol sulfate of an alcohol with up to 16 carbon atoms is used as the surface-active substance. US Pat. No. 3,342,256, published 9/19/1967, discloses that in a liquid-operated process the petroleum-displacing effectiveness of a CO 2 amount can be increased by the use of water and a foaming surfactant within this amount. US Pat. No. 3,529,668, published September 22, 1970, shows that in a liquid-operated process the efficiency of a foamed CO ₂ quantity can be increased if it is mixed with specifically composed quantities of gas and liquid. US Pat. No. 4,088,190, published May 9, 1978, shows that, in a liquid-operated process, the heat stability of the C0 ₂ foam can be increased if an alkylene sulfoacetate is used as the surface-active substance. US Pat. No. 4,113,011, published 9/12/1978, teaches that in a C0 "foam stream the problems of low salt tolerance which are encountered for the surface-active sulfates recommended by US Pat. No. 3,330,346 of polyalkoxylated alcohols having 10 to 16 hydrocarbon atoms and are typical of the surface-active alkyl sulfoacetates recommended by US Pat. No. 4,088,190, can be avoided by using a surface-active sulfate of a polyalkoxy alcohol with only 8 or 9 carbon atoms, the surface-active substance being pressed in before the CO ".
30th

The invention relates to a _{favored by CO 2} , water and surface-active substance method to internalize petroleum. to displace and / or promote half of an underground deposit that contains crude oil and brine, the deposit having to be leak-proof for liquids at a pressure at which C0 "is largely liquid.

1A-55 592

First, a polyalcoholic or phenolic surfactant is selected. This selected surface-active substance has certain properties if it is mixed a) with an oil and a brine with largely equivalent physical and chemical properties to those of the reservoir oil and the reservoir brine and b) the mixing largely at reservoir temperature and a pressure at which CO “Is largely liquefied, is carried out. In this case, the selected surface-active substance can form largely uniform and relatively stable homogeneous dispersions of the following types: 1.) CO ₂ dispersed in a solution of the surface-active substance dissolved in brine, 2.) CO 2 and oil dispersed in a solution of the surface-active substance dissolved in brine and 3.) CO "and the surface-active substance dissolved in brine dispersed within the oil.

Second, the liquid in the reservoir is circulated between the injection and exit points at a speed that _{ensures both a pressure for the substantial liquefaction of the CO 2} and a suitable flow rate, the mobility of the liquid largely corresponding to that of the reservoir brine. 25th

Thirdly, with approximately the same circulation speed, parts of the surface-active substance, the CO ₂ and the brine with largely the same chemical and physical properties, such as those of the reservoir brine, are introduced into the inflowing liquid. The sequence and volumes of these parts are chosen so that before or at least shortly after entering the deposit, the CO 2 is largely homogeneously dispersed in a solution of surface-active substance in salt solution.

1A-55 592 g.: .- .. '· .. ·· .. · "••••••• 320 3

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Fourth, the injection of CO ₂ / surfactant and brine is continued until the volume of the resulting dispersion of CO ₂ in a solution of the surfactant in the brine is sufficient to form a band or unit that is large enough to remain largely intact during its transport between the press-in and exit points within the deposit.

In order to displace oil to the outlet point, the liquid is used circulates constantly between the injection and exit points within the deposit.

The invention is described in more detail below with reference to the drawings, wherein

Figures 1, 2 and 3 show schematic representations of the above-mentioned three types of dispersions. Each of Figures 1, 2 and 3 shows schematically a viewing cell, each cell containing three superimposed layers of liquid. The upper layer of each cell consists of liquid CO 2 and the lower layer consists of a saline solution containing surfactant. The surface-active substance is indicated by a "+". The middle layer of FIG. 1 consists of a solution of surface-active substance which contains CO ₂ droplets, which are indicated by "o". The middle layer of FIG. 2 additionally contains oil droplets, which are identified by a hatched circle "©". The middle layer of FIG. 3 contains CO ₂ droplets which are dispersed in an oil solution of CO ₂ and which are unujobic with a film of the surface-active substance solution.

4 to 6 show diagrams in which the oil saturation in percent of the pore volume (% PV) is plotted against the amount of liquid (in PV) that was pressed into the oil-containing drill cores of the rock formation.

1A-55 592

Figures 7 and 8 show graphs between varying pressures (in Atm) and the amount of liquid (in PV) that are in .the oily Drill cores of the rock formation was injected.

As can be seen from the references cited above, it was previously believed that various types of surfactants or processes could be used _{in a foam stream process for oil production promoted by CO 9 and aqueous surfactant solution.} In order to avoid problems such as the sensitivity of the foam to the pressure or the temperature of the deposit, or to the salt content of the brine in the deposit, or to the long duration of the process or the like, the surfactant should contain a sulfate of a polyalkoxylated alcohol 8 or 9 carbon atoms and as an aqueous solution before the CO, - are injected. As is known, however, such as alcohol sulphates surfactants in water-containing underground reservoirs with temperatures around 6 5 ⁰ C are chemically unstable. At these temperatures, such surface-active substances are therefore hydrolyzed relatively quickly to alcohol or acids, which have a much lower surface activity.

In the method now described, a surface-active substance from a more hydrolysis-resistant class of surface-active substances, which is matched to the physical and chemical properties of the oil and brine contained in the reservoir, can be used. It is a polyalkoxylated alcoholic or phenolic surface-active substance which can form the three types of largely homogeneous dispersions described above on contact with the reservoir fluids and largely liquefied CO ₂ at the pressure and temperature of the reservoir.

1A-55 592 _Aö:: ".....: ..

The chemical stability of each surface-active substance selected in this way is significantly greater than that on the market available surface-active substances of the alcohol sulfate type. In addition, the surface-active substances so selected are also surface-active if they are in-economical low concentrations in brine, the salinity of which is between that of almost pure water and those of the almost saturated salt solutions are dissolved. The surface-active substances selected in this way have adsorptions for deposit rock, which with respect to those of the chemically stable anionic surface-active substances, such as the petroleum sulfonates, are low.

If the chosen surfactant is injected in such a way that it becomes a dispersion of CO _? Forms in a solution of the surface-active substance in brine before or soon after entering the deposits, this method can be used to select a certain pressure gradient within the rock layer through which the CO _{2 is} transported. The value of the selected pressure gradient can be in a range , which largely corresponds to that obtained by injecting CO-free brine, up to a value that is 2 to 200 times greater. During oil production, the size of the pressure gradient can be varied by relatively small changes in the concentrations and / or proportions of the liquid components to be injected.

Fig. 1 to 3 show schematic representations of the three types of dispersion, which by a suitable surface-active Substance will be formed in the event that the surfactant comes into contact with those in the reservoir containing liquids under the reservoir conditions. The phenomena of such dispersions are Easily observable in high-pressure viewing glasses if, for example, a Daniel high-pressure tube with a transparent Glass is used on both sides to allow observation of the interfaces between immiscible liquids.

1A-55 592

AA ' JzU ο Q b Z

Visual cell tests of the following types are for eligibility purposes a polyalkoxylated alcoholic or phenolic Surface-active substance suitable for a particular deposit. Become a visual cell and its contents largely on the pressure and temperature of the deposit held. A solution of the surfactant and the saline solution to be used is introduced into the viewing cell. The brine used should be a Be part of the flowing water in the reservoir to be treated or water with an equivalent salinity.

_{The CO 2} to be used and the oil can be introduced into the viewing cell and should correspond to the liquids pressed into the storage facility or contained therein.

1 to 3 show the dispersion effects which occurred during the selection of a surface-active substance for the Wasson deposit at a temperature of 38 to 43 ^° C. and a pressure between 63 and 210 atmospheres. The viewing cell was pressurized with mercury using a hand operated pressure intensifier. Measurements were made using a calibrated Heise Bourdon Tube Gauge. Coleman-purified CO ₉ was released into the cells from commercially available bottles. The brine used (with or without dissolved surfactant) consisted of synthetic Wasson injection water (SWIW) and Wasson crude oil was used as the oil. The chemical and physical properties of such liquids are listed in Tables 1 and 2.

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I / V-D D D3Z - «-
Al :. :: ·. . . "-.."
32Ö8662 Table 2 Mg / liter ⁰ C percent by weight Table 1 Wasson crude oil 75.9 "
78.0
26.1 composition of the synthetic Wasson injection water (SWIW) 138.3 Cations 201.3 Na ⁺
Ca ⁺⁺
Mg ⁺⁺ 83.9 Cl " HCO ~ co ₄ ⁼ Evaporation distribution Boiling point in
at 760 now 0.5 36.1 Number of coals
substance atoms 68.7 4th 98.4 5 125 _; 7th 6th 150.8 7th 174.1 8th 195.9 9 216 _; 3 10 235.4 11 253 _; 6th 12th 27O _; 6th 13th 286.8 14th 301.8 0.8 15th 316, 1 16 329.7 17th 342 _; 7th 5.2 18th 355.6 7.0 19th 367.6 6.6 .20 379.0 5.3 21st 389.9 4.6 22nd V 23 V 24 3.8 3.5. 3.0 V 2; 8 2.4 2; ¹ 1.8 ¹ I ⁶

1A-55 592 41 '*'. . 3 2Ü8662

Table 2a ⁰ C Wt% Number of coal
material atoms Boiling point in
at 760 mm Ir ³ 25th 400.4 1.2 26th 410.5 1.2 27 420.2 1.2 28 429 _; 6th 1.0 29 438.6 1.0 30th 447.3 Oj 9 31 456.0 0.8 32 464.0 0.8 33 472.0 0.7 34 479.0

The cell is injected with the help of an injection; measured M the saline solution and / or the surfactant solution pressed in. The cell was created with a selected menu

put under pressure
ge of CO ^ / and the equilibrium temperature was established.

After a period of about 30 minutes for equilibrium adjustment the cell was moved back and forth to mix the contents.

In a cell loaded in this way, brine and CO2 are clear liquids. When the CO ~ comes into contact with crude oil, its color changes from yellow to brownish and brown or to black (if the crude oil is black), as other heavy constituents of crude oil also dissolve in the CO ₂ . However, since there is only a single contact between C0_ and the oil in the experimental procedure used, there is no further change in color apart from a slight yellowing. When using refinery oil, such as Soltrol, the CO “liquid remains clear.

In the viewing cell shown in Fig. 1, the top layer contains liquefied CO ₂ , the bottom layer contains a solution of the surfactant ("+") in brine, and the middle layer contains a relatively stable and homogeneous dispersion of CO ₂ ~ Droplets ("o") in a solution of surfactant and brine in the absence of the oil. To examine this dispersion, the cell is _{loaded with largely equal volumes of CO 2} and the solution of the surface-active substance. Most polyalkoxylated alcoholic or phenolic surfactants are capable of forming such dispersions in most brines. In the present process, it is important that the dispersion be formed before or soon after the components enter the reservoir and that little or no oil is present in the wellbore of the reservoir. It is therefore important that the mixtures that are required for the deposit are largely homogeneous in their composition.

In such visual cell experiments, dispersions of largely liquefied CO ₂ within a brine or a solution of the surface-active substance in the brine appear as foam, although the CO 2 dispersed in this way corresponds more to a dispersed liquid than a dispersed gas.

Usually, dispersions that exist for less than 30 minutes are considered unstable and only those that remain stable for much longer are selected for use. Within the unobservable interior of the viewing cell, a small part of the liquid, which is specifically lighter or heavier than the dispersion, tends to separate above and below the dispersion layer. The brine is usually the specific heaviest liquid, the CO ₂ has the lowest specific density and the oil has a specific density between that of the brine and the oil.

1A-55 592

AS

3203662

Fig. 2 shows a suitable stable and homogeneous dispersion of CO ₂ and oil within a solution of the surface-active substance in brine. The CO ₂ droplets are identified by "o" and the oil droplets by "@". The "+" denotes the surface-active substance. In such experiments, the cell is loaded with largely equal proportions by volume of CO 2 and the surface-active substance solution in the brine and a smaller proportion by volume of the oil of 1:30, since the oil tends to destabilize such dispersions. Many surface-active substances which can form stable dispersions as shown in FIG. 1 are unable to form dispersions as shown in FIG. 2, even if the proportion of the oil is relatively small. Examples are given in Table 3.

Table 3

Commercially available surfactants capable of _{forming suitable dispersions of CO 2} in a solution of the surfactant in brine, but not of CO and oil in a solution of surfactant in brine,

trademark

or
Product name

25 Pluronic L 61 Pluronic L 92

Petronate-L

Hexadecyltrimethyl-30 ammonium bromide

Neodol 25

Saponin

35 Triton X-4 5

Naphtheny! Alcohol

composition

Block polymer made from polyoxyethylene and polyoxypropylene groups Sodium salt of petroleum sulfonates, hexadecyltrimethylammonium bromide

Aliphatic alcohol with 12-15 carbon atoms.

Amorphous glycosides

Ethoxylated isoctylphenyl with 5 ethoxy groups

Naphthenic alcohol

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1A-55 592, ...

Figure 3 shows a suitable stable homogeneous dispersion of both CO ₉ (denoted by "o") and a solution of the surfactant in the brine which are dispersed within the oil. In these experiments, the viewing cell is loaded with largely equal proportions by volume of CO ₂ and surface-active substance solution and a volume proportion of oil that _{exceeds the total volume of CO 0} and surface-active substance solution. This is a particularly accurate test for examining the formation of a single type of dispersion. The arrangement of the surface-active substance solution shown in the form of films around the CO ^ droplets is speculative. However, this arrangement seems to agree with the knowledge gained from numerous laboratory tests in oil production processes.

Table 4 lists typical commercially available surfactants that form good, decent, or poor dispersions of both CO ₉ and surfactant solution in oil. The brine had a composition of 23.98 g sodium sulfate, 4.78 g calcium sulfate and 0.8 g strontium sulfate per liter of distilled water.

1A-55 592

32ÜÖ662

Tab elle

Commercially available surfactants that form suitable dispersions of both CO ₂ and surfactant solution in brine dispersed in oil.
Trade name Rating * Composition

Neodol 25-9

Ethoxylated, 12-15 carbon atoms containing aliphatic alcohols with 9 ethoxy groups

Pluronic L 64

Block polymers from polyethylene and polypropylene groups

Pluronic L 44

Block polymers from polyethylene and polypropylene groups

Triton X-100 0 Polyethoxylated Octylphenol

(except for very salty brine)

Polytergent SL-62 0 condensation product of

(well distributed) ethylene and propylene oxides

Neodol 25-7

Ethoxylated aliphatic containing 12-15 C atoms. Alcohols with 7 ethoxy groups

Neodol 25-3S S

(too weak)

Neodol 25-3 S.

(too weak)

Sulphate of 12-15 carbon atoms containing aliphatic alcohols with 3 ethoxy groups

(see above, but not sulfated)

Alipal CD-128 **

Ammonium salt of a linear primary ethoxylated alcohol sulfate

* G = good; 0 = tidy; S = bad

** Anionic, surface-active substance (with essential lower chemical stability)

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1A-SS 592

A non-obvious and particularly important point of view in the present method is the fact that the relative mobilities or the effective Viscosities of the dispersions in FIGS. 1, 2 and 3 within permeable rock strata largely vary correspond. If in the experiment dispersions are passed through the cores of the reservoir forinations, and at the same time the pressure required to maintain a certain flow velocity recorded or the Falling times and / or falling speeds of a ball measured in a viewing cell containing the dispersions no deviations can be determined.

4 to 8 show typical results which were obtained in core flow tests with different compositions of CO 2 brine and saline solution of the surface-active substance. Very often the cores came from the Sein Andres rock, with a diameter of 7.5 cm and length 25 cm. The flow rates varied between 7.5 cm to 30 cm per day. The temperature was maintained at about 41 ⁰ C and to maintain the tube pressure of about 140 atm in the core, a back-pressure regulator was used.

4 shows the results of successive injections of A) 0.2 PV (pore volume) CO ₂ , B) 0.1 PV brine, C) 0.2 PV CO ₂ , D) 0.1 PV brine / E) 0, 3 PV CO ₂ and F) 0.3 PV brine. A SWIW solution (see Table 1) containing 0.1% by weight of the surface-active substance Neodol 25-9 was used as the brine. As FIG. 4 shows, the first 0.2 PV injection (A) of the CO «results in only a slight reduction in the original oil saturation of about 37%. The B injection of the first 0.1 PV of the saline solution causes a significant drop in the curve, which in the C injection with the second 0.2 PV amount of CO _? is continued, so that in the course of the injection of about 1 PV of liquid, which _{consists of 0.7 PV of CO 2} , the 'remaining oil saturation is reduced to about 11%.

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1A-55 592 _A Q .....

Fig. 5 shows the results obtained with a similar drill core flow, using successively 0.1 parts of PV of a brine free from surfactants ("Δ") and 0.1 parts of PV of supercritical CO ₂ ( "o") are pressed in. Although the flow rate of the flow in Fig. 5 is 30 cm per day (in Fig. 4 it was only 7.5 cm per day), in this case a lower oil production rate and a lower efficiency of the CO _{2 are} found.

Fig. 6 shows a similar flow that with an amount H of almost 2 PV of simultaneous injection of C0 _? and a SWIW solution with 0.1% by weight of the surface-active substance Neodol 25-9 begins, with CO 2 and brine in a volume ratio of 2: 1. In this case the flow rate was 27 cm per day. It can be seen that in comparison to FIG. 5, with the same sequence of CO 2 and brine, which is free of surface-active substances, an increased oil production is achieved, but that compared to FIG "Compared to FIG. 4 is smaller. The lower oil delivery rate in FIG. 6 is mainly caused by the simultaneous injection of the brine, which _{shields the CO 2} so that it cannot directly touch and displace the remaining oil. The K-injection following the H-injection consists of a Neodol 25-9 solution distributed in SWIW.

The pressure gradient between the injection and exit points in a deposit can be adjusted by relatively simple changes in the composition, for example by changing the quantitative ratio between surface-active substance and brine or between CO ₂ and brine and / or by changing the sequence of such liquids. With the help of such changes, the pressure gradient can easily be increased to a value that is 2 to 100 times higher

1A-55 592 :::

is / are regulated as that which results from the injection of the brine alone, whereby the salinity of the brine largely corresponds to that of the water in the rock layer (swept zone) of the deposit. In general, the pressure gradient decreases during the injection of the CO 2 and increases during the injection of a salt solution with a surface-active substance / the pressure gradient increasing with the concentration of the surface-active substance in this solution.
10

When the C0 ~ and the surfactant solution are not mixed with one another in the brine before it enters the deposit, the particle size should be of the alternating gas and liquid components not more than 40% of the volume sufficient for band formation be. This tape remains in the storage facility during transport between the injection and discharge points generally received. The volumes required for band formation are different for different deposits, however, they can be determined with sufficient accuracy using known methods. For example, have Laboratory tests have shown that by injecting a volume that is approximately 0.3 PV of a solution of the SWIW brine with 0.1% Neodol 25-9 (before a further injection of the C0-) through-flow drill core is a pressure gradient, which corresponds to that which is necessary to bring the brine at a selected rate into the first 0.35 PV to be able to pump in the subsequent CO "injection" achieved will. Thereafter, the press-in pressure decreases and is reduced to half or a third of what is required, respectively according to the selected flow rate of the brine. During this time the injected COp amount is approximately 0.5 PV.

5 If the CO ₂ and the aqueous brine are used successively, using amounts less than 30% of the. Maintaining an intact volume of the necessary volume, or using even smaller quantities or

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under a premix of the liquids, then they should be injected before or soon after entry be largely homogeneously mixed in the deposit. This is also because of the largely radial flow geometry necessary in the bearing point through which there is a flow. In a particularly preferred method, it is advantageous to start at the beginning an order of each volume part, with 20 to 30%

necessary volume,

the one used to form an intact band / that made from brine with surface-active substance and CO ~ exists, to be injected. This should be done before pressing a successive series of smaller quantities or one at a time Flow of these liquids take place in order to achieve an additional volume, which is necessary for band formation. That Band can then be displaced with a cheaper drive fluid.

In the present method, achieving a homogeneous mixture in the vicinity of the press-in location is particularly advantageous. The operator can select and maintain a pressure gradient necessary for the flow velocity between the press-in and exit points. The selection can be made by measuring the injection pressure, which is necessary to maintain the flow rate of the brine, or by measuring the pressure gradient necessary for the injection rate of the brine. By observing these conditions, the operator becomes nervous as soon as the band of CO ^ foam or a foam emulsion or a mixture of CO ₂ and liquid, which has a lower mobility, into a more porous rock layer (thief zone) similar to a permeable vein, through which the liquid can flow faster with the same pressure gradient. Entering this rock layer causes relatively rapid changes in pressure and / or velocity necessary to achieve a selected flow rate or gradient. By changing the composition of the inflowing liquid, the operator can

reduce the mobility of this liquid as necessary to maintain an average flow rate or gradient of a certain value.
5

7 shows a diagram in which the change in pressure (in atm) against added volumes of successively injected parts of the supercritical CO ₂ ("o") and brine / Neodol 25-9 solutions ("Δ") in a drill core flooding experiment are shown. The drill cores come from the San Andres rock and have a length of 25.4 cm and a diameter of 7.5 cm.

The drill core used for the experiment in Fig. 7 has a permeability to brine of 5.3 mdarcys, a porosity of 12.5%, a pore volume of 138 ml and, after the water flooding, a remaining oil saturation of 43.0% PV. For the experiment shown, a light kerosene with the trade name Soltrol 130 was used as the oil, which is completely miscible with C0_ at the pressure and temperature of the Wasson deposit. The brine used contained 0.1% Neodol 25-9 as a surface-active substance. The temperature was kept at 41 ^° C. / the liquids were pressed in against the counter pressure of 41 atm. The CO breakthrough was registered by direct observation of the liquids. The pressure changes (see Y-axis) were measured across the length of the drill core. Typical results of such experiments show that foams or dispersions of largely liquid carbon dioxide are formed in the vicinity of the inlet opening and pass through the drill core without clogging. The CO 2 breakthrough is generally greatly delayed at 0.2 to 0.3 PV. The remaining oil saturation was reduced to less than 15% pore volume, which is comparable to the reduction achieved by continuously injecting a significantly larger amount of CO 2, without injecting a salt solution with a surface-active substance.

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1Α-55 592 23 · - ** · '"3 2ϋβ * 662

Fig. 8 shows the change in differential pressure (in Atm) as a function of the accumulated amounts (in PV) of the injected liquids in similar flooding experiments. The drill cores come from the San Andres rock and have a length of 55 to 6 2.4 cm and a diameter of 2.5 cm. These cores are covered with Teflon tapes wrapped, rolled in aluminum foil, then between brackets made of stainless steel clamped in a Teflon tube, then inserted into a rubber sleeve and finally fixed in a triaxial core holder. The loading Core holder is fixed horizontally in a constant temperature bath and evacuated. The core then becomes saturated and its permeability to brine is determined. The core was saturation of oil with an initial saturation oil flow of 300 cm per day flows through. Then a brine solution was injected at 300 cm per day to get a to achieve water-flooded remaining oil saturation.

After reducing the flow rate to 7.5 cm per day was the back pressure is set to about 41 atm.

The curve P relates to the simultaneous injection of CO ₂ and a brine which contains 0.1% Neodol 25-9 as surface-active substance, the volume ratio being 2: 1. The velocity of the inlet flow of the combined volumes of both phases was 27 cm per day. The oil production was with the best production that by continuous. In an earlier experiment, the simultaneous injection of CO ₀ and brine, the injection of 0.3 PV brine, 0.5% Neodol (after only 0.74 PV _C0? were pressed, was preceded. As of curve P is apparent from 1,4 PV CO ₂ are needed in an attempt to achieve the same percentage.

~ " ⁵⁹²

- 2Ό -

Such comparable tests show that it is appropriate if, before the simultaneous injection of the CO ₂ and the brine with surface-active substance, at least two successive amounts of surface-active substance-containing brine and CO ₂ , the pore volumes in the order of magnitude of 0.2 to 0.3 have to be pressed in. As shown in curve P, the differential pressure increases above 14 kg / cm ² for successive impressions of 0.4 PV and reaches a maximum at around 1.4 PV.

In contrast, curve Q shows the pressure behavior that is typical for injections of CO ₂ and brine without a surface-active substance. The pressure gradient is gradually reduced during the M injection of a little more than 0.5 PV CO _2. The M injection of the brine causes a steep increase in the pressure gradient during the injection of the first 0.1 PV of the brine, but this is immediately followed by a decrease in the pressure gradient during the injection of the next 0.2 PV.

Xl Γ29

Claims (5)

3203662 »· Λ.: 'Υ ■ ·:, .- PATENTANWÄLTE.-Ur-nw .. PRa1N ^ tiIi'sthoi i *" WUESTHOFF-v. PECHMANN-BEHRENS-GOETZ "-' ''" "" ^ * « »■" »« "■ to * DIPI ..- ING. GFRHARD TUIS (19JI-I97O EUROPEAN PATENTATTORNEYS I3Ipi, c„ em. I, R. Ε. «Γ.π, κκκ from γεο.μανν DR.MNG. DIETKR BEHRENS DIPI ..- ING.J DIPL.-WIH-TSCJI.-iNG. RUPERT GOETZ SHELL INTERNATIONAL D-8000 MUNICH 90 "~ RESEARCH MAATSCHAPPIJ BV SCHW1.UGKRSTRASSE 2 Carel van Bylandtlaan 30, ,, w, ■ _, τ» ■, · JiJ phone: (089) 6610 51 The Hague, Netherlands' TELEGRAM: PROTECTPATENT 1A-55 592 TELEX = JZ4O7O Patent claims: 1. A method for transporting CO ₂ , a surface-active substance and an aqueous solution through a Ge-rock layer located between injection and exit points within an underground deposit, whereby at the same time in this rock layer a) a certain pressure gradient, b) a selected extraction rate and c) a pressure at which the C0 "is largely in the liquid state is maintained, characterized in that a polyalkoxy-alcoholic or -phenolisehe surface-active substance is selected, which can form relatively homogeneous and stable dispersions with largely equally low mobility If the surface-active substance is subjected to the reservoir temperature and a pressure which can be maintained both within the reservoir and which is high enough to substantially liquefy the C0 "at the temperature of the reservoir, and if it is mixed with an aqueous liquid, its salinity in the wes entlichen corresponds to that of the aqueous liquids of the rock layer, and mixed with an oil, the composition of which also corresponds essentially to that of the oil in the rock layer, these dispersions are present: 1) CO ₂ dispersed in aqueous surface-active substance solution, 2) CO ₂ and oil dispersed in aqueous, surface-active substance solution and 3) CO ₉ and was. Sr. surface-active solution dispersed in oil; and that J Ί U ei bb 2 1A-55 592 - Ο _ Liquids flow in and out at the injection and exit points at speeds that ensure a desired oil delivery rate and a pressure in the zone that is sufficient to liquefy the CO "if the flow liquid is an aqueous liquid whose salt content is at least largely that of the aqueous liquid in the zone corresponds; and that
the flow of the liquid continues at largely the same speed and the inflowing liquid contains proportions of CO ₂ , the selected surface-active substance and the aqueous liquid, the salt content of which at least largely corresponds to that of the aqueous liquid in the rock layer, so that with said parts before or soon after entry into the deposit, a largely homogeneous dispersion of the CO 2 is formed in the aqueous surface-active substance solution by pressing together and lining up, and that pressing in continues until the volume of the dispers ion of CO .. in aqueous surface-active substance solution is large enough to remain intact during transport through the rock layer; and that 5 the proportions and the sequence of said enclosed liquid parts during the injections be changed as necessary to avoid deviations from the selected oil delivery rate and the pressure gradient, which are maintained in the storage site rock layer should be reduced or prevented. 2. The method according to claim 1, characterized in that the inflow and outflow of the liquid 1.1 MBte, lasts for the training and exits, 5 µm during the oil extraction from the liquid that has formed, it continues to transport it through the rock layer to be able to. 3 2 0 8GG2 ·· Γ-.; / '* · .. ·. / 1A-55 592 - ^: ■ - "·· * · *"'*" 3. A _{liquid-operated process, which is favored by CO 2} and surface-active substance, for oil production from an underground storage facility which contains oil and brine and which can include the liquid at a _{pressure sufficient to largely liquefy the CO 2} , characterized in that a polyalkoxy-alcoholic or phenolic surface-active substance was selected, the properties of which correlate with those of the reservoir fluids, so that this surface-active substance can form dispersions that are relatively homogeneous at the prevailing temperature and pressure in the reservoir, with the oil and brine or with liquids that are largely equivalent to them and are stable, have approximately the same low mobilities and have the following compositions (a) C0 _? dl dispersed in a solution of the surfactant in brine, (b) CO and oil dispersed in a solution of the surfactant in brine and (c) C0 _? and a solution of the surfactant liquor dispersed in oil; and that while injection and discharge rates are maintained that are _{sufficient for a substantial liquefaction of the CO 2} pressure and a suitable oil flow between the injection and discharge lines in the deposit, whereby the circulating liquid flows a is aqueous liquid, the salt content of which corresponds at least partially to that of the brine in the deposit; and that
largely the same speeds for the injection of the liquid and the discharge are maintained and that with the inflowing liquid parts of the selected surface-active substance, CO "and an aqueous liquid, the salt content of which at least largely corresponds to that of the brine in the deposit, are enclosed; and that 1A-55 592 the volume and order of these enclosed parts are so coordinated / that before or soon after such liquids have entered the deposit, a largely homogeneous dispersion of CO 2 in the aqueous surface-active substance solution is formed, and that the inclusion of such parts of the surface-active substance, the CO "and the brine continues until the volume of this dispersion of CO" in the aqueous surface-active substance solution is at least largely sufficient to form a band that remains intact during its displacement to the exit points, and that
the pressing of liquid to displace the oil into the exit points continues. 4. The method according to claim 3, characterized in that g e k e η η ζ ei c h η e t that the enclosed parts of the upper Πüohennkl ivon substance and the aqueous liquid be pressed as a solution of the surface-active substance in this aqueous liquid. 5. The method according to claim 4, characterized in that g e k e η .n, that this inclusion by previously pressing in a volume part of the surface-active Substance solution, which is about 20 to 30% of the volume part of the tape, is effected and subsequently a C0 ~ volume of about 20 to 60% of the tape volume are pressed in, and after this pressing in a number smaller successive parts of such liquids or a largely simultaneous injection of such l'Milaüitjkt'i ten follows in order to form the remainder of the band.